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Back surface curvature and measurement of lumbar spinal motion
52 C/in. Biomech. 1988; 3: No 1 Mechanical strength of tibia1 trabecular bone evaluated by X-ray computed tomography
Back surface curvature and measurement of lumbar spinal motion
The prospects for the use of quantitative computed tomography (QCT) for evaluation of mechanical properties of tibia] trabecular bone were investigated. Computed tomography (CT) data from the proximal tibia] epi- and metaphysis of six human cadaver knees were correlated with mechanical data obtained from compression tests and penetration strength measurements. In addition CT and intraoperative penetration data were compared in 20 patients. If spatial agreement between CT and mechanical measurement sites is optimized, close correlations are found between the relative linear attenuation coefficient determined by CT and the ultimate strength (r=O&l), the yield strength (r=0.85), the elastic modulus (r=O-78). the ultimate energy absorption (r=O-83), the yield energy absorption (r=0*81), and the penetration strength (r=0.82). It is concluded that these correlations are sufficient to make QCT a valuable tool for non-invasive evaluation of the spatial distribution of bone properties in several clinical applications.
Lumbar spinal llexion and extension motion was measured radiographically and from the back surface curvature in 42 patients with low-back pain to determine whether the surface measurements provided accurate measurement of the total lumbar motion and its distribution by vertebral level. Also, a biomechanical mode1 of motion of the lumbar spine was used to predict the changes in the back surface as a function of varying amount of flexion and extension at the intervertebral articulations. Surface measurements provided reasonably accurate (+ 11.2” or +255%) measurement of the total lumbar motion with a correlation coefficient of 0.58 between surface and radiographic measures. However, there was a poor correlation (varying between -0.08 and 0.54 at different levels) between segmental motion measured radiographically and at the surface. Detection of the most mobile and least mobile intervertebral levels was done successfully by the surface curvature method in no more cases than would be expected by chance. Measurements of intersegmental motion are inherently error prone since they involve calculating differences between small angles which in turn are difficult to measure accurately. Surface measurements based on changes in back curvature are further complicated since the back surface has a variable relationship withspine shape and accurate measurement of curvature is very difficult.
Bentzen SM, Hvid I, Jorgensen J. J Biomech 1987; 20: 743-52
Analysis of the asymmetrically loaded spine by means of a continuum beam model A continuum beam model of the human spine, proposed by Hjalmars (Proceedings of the Fourth International Conference on Continuum Models of Discrete Systems, 1981), and earlier used by the present author as a tool for the analysis of mild functional scoliosis, is here used for the study of a spine, asymmetrically loaded in the frontal plane. In order to validate the theoretical predictions of the model, preliminary experiments are carried out, which show that the mode1 fairly well describes the lateral curvatures that occur when, for various loading conditions, the spine is adjusted into a muscle-relaxed state of equilibrium. Values of the flexural rigidity estimated from the experiments are found to be in reasonable agreement with values, estimated from earlier observations on dead material, reported in the literature. The experiments also indicate that the model may be developed to a tool for estimations of the effective flexural rigidity of the spine in vivo. Lindbeck L. J Biomech 1987; 20: 753-65
Stokes IAF, Bevins TM. Lunn RA. Spine 1987; 12: 35-5-61
A simple method to estimate the rib hump in scoliosis A simple device to measure the rib hump deformity in scoliosis is described. The importance of defining the plane of measurement rigidly was stressed. The visible rib humps from 30 scoliotic patients were measured in the form of plotted curves by a group of paramedical and medical staffs. Highly reproducible results were obtained. The expected difference between two curves measured on a random patient by a single investigator was O-116 cm, and the expected difference between the curves made by two random investigators on the same patient was O-167 cm. This instrument is useful in charting the progress of the rib hump deformity in daily clinical practice. Pun WK, Luk KDK, Lee W, Leong JCY. Spine 1987; 12: 342-5
Gait reaction reconstruction and a heel strike algorithm A mathematical model of gait ground loading is presented. The model allows the ground reactions produced by any particular single- or multiple-footfall pattern to be constructed, given a sufficient variety of other measured ground reactions. An algorithm which uses centre of vertical pressure data only to determine the instants of successiveheel strikes on a large force plate is then presented. Experiments show the high accuracy of the heel strike algorithm and show that reconstructions of the vertical component of ground reactions are typically within 3% of corresponding measured reactions. The techniques presented allow certain problems associated with small force plates and other problems associated with large force plates to be largely overcome. Brodland GW, Thornton-Trump AB. J Biomech 1987; 20: 767-72
Lung function in relation to thoracic spinal mobility and kyphosis Mobility and kyphosis of the thoracic spine were correlated with lung function in 185 men and 87 women not suffering from respiratory disease. Curvatures of the spine were measured goniometrically with inclinometers and a compass, and lung function by spirometry. Vital capacity and forced expiratory volume in 1 set had significant positive correlations only with forward and lateral flexion. The strongest correlations were with forward flexion (r=O-16 to O-24, ~~0.05). The results and possible advantages of mobilizing the thoracic spine in pathological conditions of the lungs and the spine are discussed. Mellin G, Harjula R. Stand J Rehabil Med 1987; 19: 89-92
Back surface curvature and measurement of lumbar spinal motion
The prospects for the use of quantitative computed tomography (QCT) for evaluation of mechanical properties of tibia] trabecular bone were investigated. Computed tomography (CT) data from the proximal tibia] epi- and metaphysis of six human cadaver knees were correlated with mechanical data obtained from compression tests and penetration strength measurements. In addition CT and intraoperative penetration data were compared in 20 patients. If spatial agreement between CT and mechanical measurement sites is optimized, close correlations are found between the relative linear attenuation coefficient determined by CT and the ultimate strength (r=O&l), the yield strength (r=0.85), the elastic modulus (r=O-78). the ultimate energy absorption (r=O-83), the yield energy absorption (r=0*81), and the penetration strength (r=0.82). It is concluded that these correlations are sufficient to make QCT a valuable tool for non-invasive evaluation of the spatial distribution of bone properties in several clinical applications.
Lumbar spinal llexion and extension motion was measured radiographically and from the back surface curvature in 42 patients with low-back pain to determine whether the surface measurements provided accurate measurement of the total lumbar motion and its distribution by vertebral level. Also, a biomechanical mode1 of motion of the lumbar spine was used to predict the changes in the back surface as a function of varying amount of flexion and extension at the intervertebral articulations. Surface measurements provided reasonably accurate (+ 11.2” or +255%) measurement of the total lumbar motion with a correlation coefficient of 0.58 between surface and radiographic measures. However, there was a poor correlation (varying between -0.08 and 0.54 at different levels) between segmental motion measured radiographically and at the surface. Detection of the most mobile and least mobile intervertebral levels was done successfully by the surface curvature method in no more cases than would be expected by chance. Measurements of intersegmental motion are inherently error prone since they involve calculating differences between small angles which in turn are difficult to measure accurately. Surface measurements based on changes in back curvature are further complicated since the back surface has a variable relationship withspine shape and accurate measurement of curvature is very difficult.
Bentzen SM, Hvid I, Jorgensen J. J Biomech 1987; 20: 743-52
Analysis of the asymmetrically loaded spine by means of a continuum beam model A continuum beam model of the human spine, proposed by Hjalmars (Proceedings of the Fourth International Conference on Continuum Models of Discrete Systems, 1981), and earlier used by the present author as a tool for the analysis of mild functional scoliosis, is here used for the study of a spine, asymmetrically loaded in the frontal plane. In order to validate the theoretical predictions of the model, preliminary experiments are carried out, which show that the mode1 fairly well describes the lateral curvatures that occur when, for various loading conditions, the spine is adjusted into a muscle-relaxed state of equilibrium. Values of the flexural rigidity estimated from the experiments are found to be in reasonable agreement with values, estimated from earlier observations on dead material, reported in the literature. The experiments also indicate that the model may be developed to a tool for estimations of the effective flexural rigidity of the spine in vivo. Lindbeck L. J Biomech 1987; 20: 753-65
Stokes IAF, Bevins TM. Lunn RA. Spine 1987; 12: 35-5-61
A simple method to estimate the rib hump in scoliosis A simple device to measure the rib hump deformity in scoliosis is described. The importance of defining the plane of measurement rigidly was stressed. The visible rib humps from 30 scoliotic patients were measured in the form of plotted curves by a group of paramedical and medical staffs. Highly reproducible results were obtained. The expected difference between two curves measured on a random patient by a single investigator was O-116 cm, and the expected difference between the curves made by two random investigators on the same patient was O-167 cm. This instrument is useful in charting the progress of the rib hump deformity in daily clinical practice. Pun WK, Luk KDK, Lee W, Leong JCY. Spine 1987; 12: 342-5
Gait reaction reconstruction and a heel strike algorithm A mathematical model of gait ground loading is presented. The model allows the ground reactions produced by any particular single- or multiple-footfall pattern to be constructed, given a sufficient variety of other measured ground reactions. An algorithm which uses centre of vertical pressure data only to determine the instants of successiveheel strikes on a large force plate is then presented. Experiments show the high accuracy of the heel strike algorithm and show that reconstructions of the vertical component of ground reactions are typically within 3% of corresponding measured reactions. The techniques presented allow certain problems associated with small force plates and other problems associated with large force plates to be largely overcome. Brodland GW, Thornton-Trump AB. J Biomech 1987; 20: 767-72
Lung function in relation to thoracic spinal mobility and kyphosis Mobility and kyphosis of the thoracic spine were correlated with lung function in 185 men and 87 women not suffering from respiratory disease. Curvatures of the spine were measured goniometrically with inclinometers and a compass, and lung function by spirometry. Vital capacity and forced expiratory volume in 1 set had significant positive correlations only with forward and lateral flexion. The strongest correlations were with forward flexion (r=O-16 to O-24, ~~0.05). The results and possible advantages of mobilizing the thoracic spine in pathological conditions of the lungs and the spine are discussed. Mellin G, Harjula R. Stand J Rehabil Med 1987; 19: 89-92